Automatic telephone system



Uc. 29 WM www@ R. W. ENGSBERG AUTOMATIC TELEPHONE SYSTEM Filed Sept. 29, 1923 Jpg t and State of Illinois,

such secondar appreciated t at 1t is necessary to do this,

since if calls were permitted to arrive at a' group of secondary line switches when no trunks were available outgoing from' such the primary master switches Acomplete cycle of op interval a large number of picked -up could be plunged into bank con- BALPH W. ENGSBERG, OF 0. PK, ILLINOIS, ASSIGNOR TO AUTOMATIC `AFJ'JIEICTJR;,IG- COANYyOF CHICAGO, ILLINQIS, ACORPQRATION 0F ILLINOIS.

annuo t rre TELEPHONE SYSTEM.

Application filed September 29, 1923. Serial No. 665,530.

To all whom t may concern.'

Be it known that I, RALPH W. lENesnRo, a citizen of the United States of America, and a resident of Oak Park, Cook County, have invented certain new and useful Improvements in Automatic Telephone Systems, of which the following is a specification.

The present invention" relates in general `1o to automatic telephone systems, but more especially to large automatic systems which employ both primary and secondary line switches for the purpose of connecting calling lines with idle rst selector switches, and may be considered as an improvement on Patent No. 1,275,186, issued to WV. E.

Lamb, Au ust 6 1918, and a pendin a plication ofl. G. ,Martim Serial No. QId-GS, filed March 15, 1921.

In systems of the above kind it is necessary to make all trunk lines incoming to a I group of secondary line switches busy .whenever all| of the trunk lines outgoing from group are in use. lit will be group, it would inevitably happen that such calls would .be lost, i. e., they could not be a successfully completed. llt is also necessary to provide means whereby the primary mastei switches are caused to pick up allfthe p-lungers'gpof their respective idle switches and bring them into locking engagement with their plunger shafts to prevent the possibility of such switches plun ing in on busv trunks. This is accomphsheby causing all to go thru a the trunk lines leading out of a secondary group become busy.

The arrangement show-n in the above lpatent for accomplishing this latter result has proven objectlonable owing to the lapse of time between the operation of the first and last of the groups(A of primary master llt will be seen that during this plungers not yet switches.

tacts of trunks extending to the busy secondary group. A further objectionis that since all groups of secondary switches have their pickup conductors permanently tied neously,

eration each time all` to a common conductor, trouble on one of these conductors is not readily located.

In the arrangement shown in the above referred to application the operating conductors of all primary master switches, and the pick up conductors of all secondary groups are connected thru separate keys to a common conductor. A buzzer is associated with these keys in such a manner that should a permanent ground occurA on either the operating or the pick up conductors, the grounded conductor may be quickly found by operating the keys in succession, the buzzer 'not'operating when thegrounded conductor is disconnected.

n The latter scheme has certain advantage over that of I' the patent in that all primary master switches are operated trouble is provided. Ithowever has'the great disadvantage of having/all of the operating conductors of the primary switches tied togetherand, therefore,

if oneyof these conductors become grounded all primary master switches will operate regardless of whether a secondary'trunk grou isbusyor not. Another objection is the liigh manufacturing cost due to the large number of keys and panel which are required.

The primary object of the invention there-` fore, is to provide simplified apparatus for 'accomplishing the. above `desired resultsy which may be manufactured more economically .than any apparatus heretofore used.

Another object is to. so design the apparatus that trouble on any particular'primary group of master switches will not a`ect the proper operation of any other primary group.

A still further object is to provide means for immediately locating a grounded conductor extending from a secondary group by the operation of'a single key, which at the same time, preventsv the continued operation of all primary master switches.

The foregoing features will be described hereinafter with reference to the accompanying figure of drawing, which shows sufficient o the apparatus in an automatic telephone system to' enable the invention to be explained and understood.

Referring to the drawing more in de- `tail, the reference character A y l simultaand a convenient method of finding ordinary type having the usual talking instrumentalities and a calling device S for controlling theautomatic switches at the exchange. The line conductors 11 and 12 terminate at the exchange in the individual line switch C, which is a line switch of the well known Keith or `plunger type, and hence will not need to be described in detail. Briefly stated the function of the line switch C is to extend the associated line when calling .to an idle trunk line. In accordance with the usual practice, the lines entering the exchange are divided into groups, and all of the line switches associated ywith the lines in each group may be controlled in their trunk selecting operations ,by a common master switch. The

vlmaster switch which is associated with the group which includes the line switch C is shown in thelower left hand corner of the sheet and is indicated by the reference character E. This master switch is of the well known solenoid type such as is in common use in the automatic telephone exchanges throughout the country.

Secondary line switches are employed in y'the present system and accordingly the trunk lines from the primary line switchboards will extend to secondary line switches rather than to- `lirst selector switches. The arrangement of the trunking between the. rimary and secondary line switchboar s is well understood. There may be a plurality of groups of secondary line switches and each grou of primary line switches will have outgoing trunks extending to secondary line switches in each secondary group, so that any calling subscriber will be given access to the trunk lines outgoing from all oflithe secondary groups. In

this manner a large number of first selectors, say one hundred or more, may be combined in one large group thus securing an increased trunkin efficiency. The advantages gained by t e use of secondary line switches, however, are well known and need not be discussed in detail. One of the trunk lines outgoing from th primary group which includes the line switch C is shown in the drawing, and extends to the secondar line switch l). The line switch D is of t e well known rotary type, having wipers which normally sta-nd on the trunk line last used, and which move 1n a forward direction only. There are a number ci relays and lamps in the` lower p right hand portion of the drawing which times.

have certain functions to perform when all of the trunk lines outgoing from the secondary line switch group which includes the line switch D become busy, and at other Tt will be convenient,` however. to go into this later on during the explanation of the operation'of the system.

Having described the apparatus involved n particular features of novelty disclosed herein. For this purpose it will be assumed that the subscriber at substation A desires to call some other subscriber in the system, and the operation of the rimary and secondary linc switches C and in connecting the line of substation `A to a trunk line extendin to a filstselector switch will be described. Vhen the receiver is removed at substation A a circuit is completed over the line conductors 11 and 12 for the line relay 16 of the line switch C. Upon energizing, the line relay 16 closes a circuit for the pull in winding 18 of the line switch at armature 25. Upon energizing, the pull in winding operates both the cut-0E armature 24 and the plunger.arm

23, the former being effective to disconnect the line conductors 11 and l2 from the winding of the line rela-y and from the grounded common conductor 46, respectively; while the latter forces the bank springs 30, 31, 32, and 33 into engagement with contacts 34, 35, 36, and 37, respectively. By the engagement of bank springs 30 and 33 with contacts 34 and 37, the line conductors 11 and 12 are extended into connection with the i ductor 41, contact 35, bank spring 31, and Athe holding winding 17 of the line switch C to battery. This holding circuit is established before the slow acting line relay 16 of the line switch C has time to deenergize and is `e'ective to retain the plunger arm 23 and the cut-oill armature 24 in operated position. A ground potential is also placed on theprivate normal conductor 15 which extends to multiple test contacts in the banks of the connectors which have access to the line of substation A, whereby the line is guarded against intrusion in the customary manner. Another circuit closed by the operation of the line switch C is completed by the engagement of bank spring 32 with con, tact 36. This places a ground on conductor` 43 and a circuit is thus completed by way of the master switch test wiper 108 and the left-hand winding of the starting relay to battery. Relay 100 is accordingly energized and at its left-hand armature completes a circuit for the locking relay` or magnet 101. As is well understood, when the locking relay is energized it releases the master switch rshaft (controlling all the idle line switch plungers) and the shaft instantly namens `pear that these test wipers will immediate e moved oil from their associated tenth test contacts and into engagement with the associated ninthtest contacts. Assuming that the ninth trunk line is idle, there will be' no ground potential on the ninth test contacts,l

the starting relay 100 will deenergize to open the circuit of thev locking relay 101, and the latter relay will de energize to again lock the master switch'shaft. lt may be pointed out in this connection that when the locking relay 101 is energized it closes a circuit for the open main relay 103 which disconnects the common conductor 44 from thenongrounded pole of the battery. This is to prevent the voperation of any other line switches while the master switch shaft is being moved from y one trunk to another b the master switch.

Continuing now withI the operation of the secondary line switch D, when the line relay 50 is energized as explained hereinbe- -fore, it closesa circuit at its armature 54 which includes the winding of the switching relay 51 and the Winding of the stepping magnet 52 in series, while at the Sametime by means of armature 55 the test wiper 66 is connected toA this circuit at a point midway between the said relay and the said magnet. The operation now depends upon whether the trunk vline with which the line switch wipers arc associated is busy or idle. lf this trunk` line is busy there will be a ground potential on the test contact engaged loy test wiper 66, such as 'test` contact 69 for example, the switching relay 51 will be short circuited, and the stepping magnet' 52 being' supplied with direct ground via the test wiper will 'operate 4rin the manner, of a buzzer to advance the switch wipers step by step in search of an idle trunk line. This movement will continue as long as the test wiper 66 continues to engage grounded test contacts. When the wipers arrive at an' idle trunk line, which we may assume is 'the trunk line comprisingv conductors 77, 78, and 7 9, the test wiper 66 will find n'o ground potential on the test contact 72, the rotation of the switch will cease and the switching relay 51 being no longer short circuited will ener ize in series with the stepping magnet 52,' t e latter remaining inoperative on account of the high resistance oit the switching relay. Upon `energizing, relay 51 connects the incoming release trunk conductor 41 to the-test wiper 66 by means ofarmature 58, and at armature 57 connects its own@ lower terminal to the now continuous conductor extending trom the test wiper 66 back over conductor 41 to the line switch C. 'lheline relay 50 be- `lected trunk line terminates.

.itt

ing still energized, the test wiper 66 is connected to ground by these operations in or der to rendery the selected trunk line busy. In addition to the foregoing, at armatures 56 and 59 relay 51 disconnects the incoming trunk conductors 40 and 42 from the windings 'of the relay 50 and from ground, re-

spectively, andt extends them by way of' wipers and 67, bank contacts 71 and 73 and conductors 77 and 79 to the line relay of the first selector switch in which these- Although this switch is not shown,`its operation is well understood-and it will be sufficient to state that the line relay of the selector is energized over the circuit of the calling lin/e and closes a circuit for the associated slow acting release relay. The latter relay, upon energizing, places a ground potential upon the release trunk conductor 78, thereby establishing a holding'circuit `for the switching relay 51 of the secondary line' switch D, and for the holding winding 17 of the primary line switch C. This holding circuit, it willl be understood, is established before the slow acting line relay 50 has had time to deenergize.

` rlhe remainder of the operations in vwhich the calling subscriber controls the .first ,se lector taken for use, and a plurality of other automatic switches through the medium of his calling device S, to complete the connection to 'the desired called line, areV well understood and as they have nothing lspecial to do`with the present invention, these oper-I ations will not be further considered, except to say that when the calling subscribe;` has finished talking, the restoration of his receiver to the switch-hook causes the automatic switches to restore to normal with the result that ground is disconnected from the release trunk conductor 78. rllhis operation breaks the holding circuit for the primary and secondary line switches C and D and the said switches arev restored to normal position, it being understood that the restoring operation of the secondary line switch D consists merely in the deenergization of the switching relay 51. v

As previously pointed out, it is necessary 'to make all trunk lines incoming to a group of secondary line switches busy whenever all of the trunk lines outgoing if'rom such secondary group become busy. The arrangement for accomplishing this in the present case is thesame as the method used in the pending applica-tion previously referred to, and consists of a series of chain relays 80, 81, etc., .and control relays 83, 84'and 85. Thereisl one chain relay for each trunk outgoing from a secondary group. rihese chain relays are connected, one to each of the release trunk conductors and as fast as the trunk lines become `busy will energize, and when all of the trunk linesare busy all of the chain relays will be energized, with the result that ground is placed on the conductor 82, thus closingan energizing circuit for the relay 83. Upon energizing, relay "83 closes at armav ture 89. a circuit for relay 85., which upon Aattracting its armatures connects ground to the' conductor 93. The release trunk conductor 41 of the trunk line which terminates in the secondary line switch -D A"is normally connected to the conductor 93, and if the trunk line is 4not otherwise engaged it is made busy anyway. Relay `85 may be a large multiple contact, or gang relay, or a number Vof relays connected in series or parallel may be used; a-t any rate, at they same time that conductor 93 is grounded l similar conductors extending to all of the remaining secondary line switches in the same group are rounded also, thus making all of the trunk ines incoming to the group in questionbusy.

As a further result of the energization ,of relay 83, upon alll of the trunk lines becomin busy, the conductor 92 is groundy ed for t e purpose of bringing about the operation of the'masterl switches in allof the primary groups from which trunk lines lead tothe question. mally energized, but when relay 83 attracts its armature the circuit of relay 84 is brokenarticular secondary group in z Relay 84, however, does not retract its ,armature immediately and in the meantime relay 83 `places ground on conductor 92 by meansof its armature 88. `The grounding of conductor 92 'is ,only momentary as ground is taken otlat armature 86 as soon as relay 84 falls back. When conductor 92 is grounded in this manner a circuit is com pleted for relay111.` This circuit extends-` ;from the grounded conductor'92, lamp L',

conductor 200 and the windin of relay 111 A vto battery. The resistance o relay 111 is such that lamp L does not glow over this circuit. Relay 111, however, operates'and, lat its armature 112 applies ground to the operating conductor 94 of each of the primary master switches, ythereby completing a circuit for relay 102 in each suchswitch. Upon energizing, relay 102 establishes a locking circuit for itself 'at its armature 120 and atits armature 121 closes the cir- T e slow acting relay 84 is nor which time they-line switch plungers will be op osite the` irst'trunk.y The arm 122 now c oses contact springs 124 and 125, thus .completing a circuit for relay 104. When relay 104 attracts its armature, the armathe tooth on sprin remains in operate position after its energizin circuit is broken. The energization of re ay 104 breaks theI locking circuit of relay 102, ermitting this relay to fall back, and also c oses a new circuit for the locking -rclay 101, in orderv that this lattery relay may be held up after the relay 102 has deenergized. In addition, relay 104 closes a. circuit for the solenoid 106. Upon the eneryture is lockedin operated position behind 126 so that the relay gization 4of the solenoid, the master switch shaft is rotated by a continuous movement in a clock-wise direction until all of the plungers are lined up opposite the tenth trunk, wipers 107 and 108 being restored to the position shown in the drawing. The arm 123 now disengages spring 126 from the armature of relay 104 and this armature is released to break Athe circuit of the solenoid 106 Iand the circuit of relay 101. Relay 101 now deenergizes and locks the shaft in position opposite the tenth trunk.- Obviouslywhen the primary master switches are operated, .any line switch plungers which happen to be'disengaged from the shaft `are pickedup and are again brought under the control. of the master' switchA so that there will be no danger of 'any of them being plunged in on busy trunk lines.

The features of the invention lie in the provision and arran ement of multi-contact relay 111, key K2 an lamps L., L2, etc., the purposes of which will now be fully explained. Assuming there are five groups of secondary line switches, and twenty-live or more groupsof primary line switches, it will be clear thatthere will be fivebranches correspondin to conductors 92, and twentyive or more4 ranches corresponding to conductor 94. It will be evident that since the conductors 94 are connected together momentarily, `only when all of the primary switches are to be operated, that should a conductor 94 become locally grounded only the one primary master switch will be operated and consequently only the subscribers associated with that particular group will be unable to complete connections. Since only one primary master switch will be continuously |bperating when the usual alarm signal notities the attendant of trouble the master switch in trouble may be readily lof cated.

lrelay 111 and the resultant continued opnaraaaa eration of all primary master switches. 'lhe operator upon receiving the appropriate alarm simply operates key K to the left thereby opening the circuit for rela 111 causing the master switches of all `primary groups to stop as soon as they haveA com.

pleted a cycle of o eration. 'llhe key also at the same time c oses acircuit for any lamp Lf, L2, etc., associated with a grounded conductor7 therebyinforming the attendant where the trouble lies. A

"ll`he key K, in laddition to being used for locating grounded conductors 92, may also be operated to the right, in Awhich .case it functions as an emergency pick up key, and is useful to the attendant for trying the operation of the v primary master switches, and may also be used in case the regular circuits for automatically operating these master switches should get out of order. The exchangeI is always equipped with various supervisory signals and alarms which indicate the blowing of fuses or the busy condition of trunksgroups, etc. 'lhe attendant is thus, at all times, aware of they condition of the equipment and in icase Some of the automatic devices fail to perform their functions he may accomplish the desired results by means of-key K.

lln case all 'of the trunks outgoing from the primary line switch group are busy all of the test contacts in the bank associated with test wiper 107 will be grounded, and the starting relay will remain energized as long as this condition exists'.l When relay 100 is energized it closes a circuit for the locking relay 101 in order to initiate the operation of the master "switch as previously explained.

Having described the invention, what is considered to 'be new and is desired to have protected by Letters Patent will be pointed out in the appended claims.

'What is claimed is: l

1. ln combination, a relay, a plurality of branch operating circuits for said relay, lamps included in series with said circuits, means for momentarily applying a potential to any one et said branches-to cause the operation of said relay, and means for simultaneously removing all ot said branches from connection with said relay should said potential remain on any branch, said last means also effective to close a circuit for the particular lamp associated with the branch haviing a potential thereon.

2. lin combination, a relay, a plurality of branch operating conductors permanently tied together thru lamps connected in series with said relay, means for momentarily applying a ground potential to anyv of said branches to operate said relay, and means lor causing any of said lamps which are connected to a branch having a ground pofrom said circuit and substituting a poten-` tial for causing any lamp to glow which is associated with a branch conductor having a potential thereon.

4. lln a telephone system, primary line switches divided 4into groups, a master switch forcontrolling each group of line switches, secondary line switches divided into groups, trunk lines leadingfrom said primary to said secondary linev switches, secondary trunk lines groups of Ysecondary line switches, a relay for completing operating circuits for each of said master switches,andI means operable rwhen all the secondary trunk lines leading from any group are in use for causing a momentary operation of said relay.

5. In a telephone system, primary line switches divided into groups, a master switch for controllingr each groupof line switches, .secondary line switches divided into groups, trunk lines leadingfrom said primary to said secondary line switches, secondary trunk `lines leading out of said groups of secondary line switches, a circuit for causing each of said master switches to sweep over all of the trunk lines of its respective group of primary switches while some of said last trunksI are idle, a relay for causing said circuit to be completed, and means operable when all of the secondary trunk lines outgoing from any group are vin use for causing the operation of said relay.

6. lln a telephone system, primary line switches divided into groups, a master switch for controlling each group of line switches, each such master switch having an operating conductor, a multi-contact relay for simultaneously tying together and grounding all of said conductors to cause Isaid switches to operatefsecondary line switches divided into groups, trunk lines leading from said primary to said secondary line switches, secondary trunkflines leading out of said groups of secondary'line switches. and means forcausing the operation ot said relay when all the secondary trunk lines of a group are in use. L

lln witnessl whereof, l hereunto subscribe my name this 26th day of September,

RALPH W. ENGSBERG.

dit

leading out of said uit 

